Electrode assembly



'Feb."15, 1938. T J HENRY 2,108,533

ELECTRODE ASSEMBLY Filed Feb. 27, 1937 INVENTOR THOMAS J HENRY ATTORNEY Patented Feb. 15, 1938 ELECTRODE ASSEMBLY Thomas J. Henry, East Orange, N. J., assignor, by mesne assignments, to Radio Corporation of America, a corporation of Delaware Application February 27, 1937, Serial No. 128,091

shown in detail in Figure 2, each of which is attached, in this particular embodiment of the invention, to the upper end of one of the exten- 2 Claims.

My invention relates to electron discharge devices, and more particularly to filamentary cathode tubes subject to microphonic and other tube noises, such as hiss.

It has been proposed to lessen microphonic and similar disturbances in tubes employing filamentary cathodes by damping the center sections of the filament to lessen vibration. For example, insulated hooks have been attached to the grid side rods to engage the filament intermediate its ends. It has been found that tubes having vibration damping means for the filament often have considerable tube noise, known as hiss, apparently caused by erratic fluctuations in emission current.

The principal object of my invention is to make an electrode mount with a filamentary cathode in which the microphonic and hiss noises are minimized.

An electrode assembly embodying my invention comprises a filamentary cathode surrounded by a grid and an anode, an inverted V-type filament, according to one embodiment of my invention, being supported at the lower end of the assembly by current supply lead-in conductors and at the upper end of the assembly by a resilient support. Substantially mid-way between the ends of the assembly are insulated side hooks which engage the legs of the filament. An electron shield surrounds the filament in registry with the side hooks and between the hooks and the anode to modify the electrons flowing to the anode from the cooled section of the filament.

The novel features which are believed to be characteristic of my invention are set forth with particularity in the appended claims, and one embodiment of the invention is described in the following specification and may be readily understood by reference to the accompanying drawing in which Figure 1 shows in section one tube embodying my invention and Figure 2 shows in detail a filament side hook.

Envelope I with re-entrant stem 2 encloses an electrode assembly or mount comprising an oxide coated filamentary cathode 3, wire wound grid 4 with side rods 5, and anode 6. The filamentary cathode shown by way of example as an inverted V, is attached at its lower ends, preferably by metal tabs, to current supply conductors l and is supported at its upper end by a resilient filament support 8 attached to rod 9 embedded at its lower end in the press. To prevent vibration of the filament and disturbing microphonic noises during operation, each leg of the filament is engaged intermediate its ends by hook l0,

sions l of the filament lead-in conductors.

present.

While the precise cause of the hiss is not known, it is my belief that the filament at the points of low temperature is a temperature saturated emitter, the emission being free of space charge limitations and sufficiently erratic to cause the disturbance.

It is well known that the fluctuation noise per unit of anode current from a temperature saturated emitter is in general greater than that from a space charge saturated emitter.

To eliminate the effect of erratic electron emission from the cooled sections of the filament, I propose to shield the anode from the hiss producing stream of electrons.

In the particular embodiment illustrated in the drawing, the shield comprises a number of closely spaced grid windings I l opposite the filament side hooks. The turns of the grid are sufiiciently close together that with normal operating potentials the amplification factor of this section of the grid is so high substantially no current from the cooled section of the filament reaches the anode.

Tubes known as type RCA-4564 with the control grid having 6 turns wound with a pitch of turns per inch opposite the side hooks and with the remainder of the turns wound with a pitch of 25.5 turns per inch have been found to have substantially less microphonic disturbances and hiss noises.

Many modifications may be made in mounts embodying my invention without departing from the scope thereof.

For example, the shield may ductors.

It is, accordingly, desired that my insurrounding said cathode, and an anode surrounding said grid, steadying means engaging said cathode intermediate the ends of the electrode assembly, means to prevent flow of emission current to the anode from the section of the cathode engaged by said steadying means comprising close spaced turns of said grid in registry with said steadying means and between said steadying means and the anode, said turns being more closely spaced than the remainder of 10 the turns.

THOMAS J. HENRY. 

